Generally, the tone-quality performance of an earphone in the market is fixed, that is, the tone color and frequency response characteristic of the earphone is decided when leaving the factory. As a result, after purchasing an earphone, a user can at most adjust the playing device, and cannot adjust the earphone.
However, the adjustment of the playing device is only a digital correction and cannot satisfy a consumer pursuing high tone-quality performance. Furthermore, not all playing devices used by consumers have the tuning function. Therefore, a consumer may possibly need to purchase many different earphones to experience different tone quality characteristics, resulting in increased consumption cost and inconvenience in use.